Liquid crystal beam control devices are known in the art. Some such devices typically use patterned electrodes over an LC cell to create a spatial variation in the index of refraction that is useful to control a beam. To keep voltages low, electrodes can be placed on cell substrates on an inner side or sides thereof. To increase optical performance, the (form factor) size and/or aspect ratio of beam (control) shaping elements, defined mainly by the ratio of the patterned electrodes pitch and the thickness of the LC, should be carefully chosen. Various problems exist, including: a limited degree (extent) of angular control, poor (quality) beam intensity distribution, excessive color separation, high cost of manufacture, unsuitable operation voltage, etc.
However, now specific applications are emerging that might benefit from such elements. There are many examples of such applications, which may be qualified as “dynamic” or “smart” lighting. For example, Light Emitting Diode (LED) sources (with relatively small divergence and emitting surface) are increasingly used in the architectural lighting, automotive industry, etc., but in the large majority of cases the parameters of those illumination systems (such as diffusion, divergence, glares, direction, etc.) are fixed. At the same time, it might be extremely useful, for example, to have a lighting system that might change the divergence angle of the LED illumination system automatically when there is a car moving in the opposed direction (to avoid disturbing its driver). Other examples may be mentioned for optimized residential or general architectural lighting. In addition, with the penetration of Li-Fi technologies (replacing the Wi-Fi by smart LED sources) the ability to controllably steer or broaden light (used both for illumination and connectivity) may be very useful. This is a reason why LC beam control devices become increasingly important.
Usually the efficiency of beam shaping in LCs is defined, first of all, by the optical path difference (or the phase delay δϕ=L·δn·2π/λ, where L is the effective thickness, δn is the electrically induced refractive index difference and λ is the light wavelength in vacuum) undergone by light traversing the LC layer. This difference is limited by the maximal values of optical birefringence Δn(δn<Δn) and the thickness L of the LC. The beam shaping efficiency is also inversely proportional to the clear aperture (CA) of the element that is defined by the gap g between various electrode segments. In addition, the non-locality of the electric field distribution (fringing field, etc.) as well as of the reaction of the LC (to that electric field) impose limitations on the choice of the geometrical factors of the cell. Thus, the ratio r=δϕ/CA is one (among others) important factor (it contains also the aspect ratio L/CA or L/g). That is the reason why the thickness of the LC layer and the gaps g must be chosen in a way to increase the efficiency of beam shaping (for example, large LC thickness values L usually increase the value of δϕ, but too large of a thickness L combined with too small of a gap g between electrodes will not generate strong modulation depth. On the other hand, too large of a gap g for a small of a thickness L also will reduce the modulation efficiency). That is why an optimized choice of the ratio r is desired for each application. Once the right value of r is found, multiple such segments may be combined to “fill” the clear aperture of larger beam shaping devices. Finally, given the strong anisotropic character of LCs, the propagation of light in LCs is often accompanied by dramatic transformations of light polarization. This is the reason why it is very important to understand those transformations and to design carefully the electro optic cell (electrodes, gaps, thicknesses of the cell, etc.) to obtain the desired beam shaping. One application of such beam shaping devices is for lighting in which the light from a light source, such as a beam from an LED light source, can be modulated from a spot beam to a slit or fan beam and/or to a broad flood beam.